It is known for the thermal energy contained in the exhaust system and/or exhaust recirculation system (EGR system) of an internal combustion engine to be converted into mechanical energy.
German Patent Publication No. DE 10 2009 020 615 A1 discloses an apparatus for utilising exhaust gas heat in a motor vehicle with a circuit utilising exhaust gas heat where the working temperature of a working fluid of the circuit utilising the exhaust gas heat is regulated. In this case, the working temperature of a mass flow of the working fluid flowing through the heat exchanger of the circuit utilising the exhaust gas heat is adjusted in such a manner that the maximum permissible working temperature of the working fluid is not exceeded.
European Patent Publication No. EP 2 249 017 A discloses a similar facility for utilising waste heat with an evaporator for absorbing waste heat from an internal combustion engine where the flow rate of the working fluid is regulated in such a manner that the working fluid that is vaporised in the evaporator reaches a heater arranged in the exhaust gas flow in a superheated state when the working fluid enters the evaporator at or below a specified flow rate at which the working fluid is able to absorb a specified maximum amount of heat. The flow rate of the working fluid is controlled in such a manner that above the specified flow rate the working fluid floods the evaporator and is vaporised in the heater and then reaches a superheated state.
European Patent Publication No. EP 1 431 523 A1 discloses a temperature control facility for an evaporator, with the vapour generated by using the exhaust gas heat of an internal combustion engine. The working temperature of a working medium is controlled by altering the mass flow of the working fluid as a function of at least one operating parameter. The publication describes a classic control structure consisting of a feed forward control system (F/F feed forward correction) plus control device (F/B feed back correction). The F/F correction is calculated, but not corrected, as a function of the exhaust gas mass flow and the exhaust gas temperature. F/F correction is based on the generation of the difference between the setpoint and the actual vapour temperature.
Other facilities for utilising exhaust gas heat are known from the Japanese Patent Publication No. JP 2008 231 980 A and Japanese Patent Publication No. JP 58 023 210 A.